A general circuit design is described for the transient hot‐strip method which is presently used for studies of electrical properties of thin metal films and for measurements of thermal properties of insulating solids and liquids. It is demonstrated that a low driving voltage can be used for thin films having comparably high resistance, and that the output of power in the strip source (being the nonlinear component of the circuit) can be kept constant throughout the transient recording. The experimental arrangement for constant power conforms with the assumptions of the theory for the method and extends its validity to substantially larger temperature increases of the nonlinear resistance.